Mushroom poisoning

Mushroom poisoning (also known as mycetism or mycetismus) refers to harmful effects from ingestion of toxic substances present in a mushroom. These symptoms can vary from slight gastrointestinal discomfort to death. The toxinspresent are secondary metabolites produced in specific biochemical pathways in the fungal cells. Mushroom poisoning is usually the result of ingestion of wild mushrooms after misidentification of a toxic mushroom as an edible species. The most common reason for this misidentification is close resemblance in terms of colour and general morphology of the toxic mushrooms species with edible species.

To prevent mushroom poisoning, mushroom gatherers need to be very familiar with the mushrooms they intend to collect as well as with any similar-looking toxic species. In addition, edibility of mushrooms may depend on methods of preparation for cooking. Collectors also need to be well aware that edibility or toxicity of some species varies with geographic location.

There are many folk traditions concerning the defining features of poisonous mushrooms.[1][2] However, there are no general identifiers for poisonous mushrooms (only guidelines to identify mushrooms themselves exist, if one knows what mushroom is toxic), and so such traditions are unreliable guides. Use of folk traditions to try to identify edible mushrooms is a frequent cause of mushroom poisoning.

Examples of erroneous folklore “rules” include:

  • “Poisonous mushrooms are brightly colored.” – While the fly agaric, usually bright-red to orange or yellow, is narcotic and hallucinogenic, there have been no reported human deaths; the deadly destroying angel, in contrast, is an unremarkable white, and the deadly Galerinas are brown. Some choice edible species (chanterelles, Amanita caesarea, Laetiporus sulphureus, etc.) are brightly colored, while most poisonous species are brown or white.
  • “Insects/animals will avoid toxic mushrooms.” – Fungi that are harmless to invertebrates can still be toxic to humans; thedeath cap, for instance, is often infested by insect larvae.
  • “Poisonous mushrooms blacken silver.” – None of the known mushroom toxins have a reaction with silver.
  • “Poisonous mushrooms taste bad.” – People having eaten the deadly Amanitas reported that the mushrooms tasted quite good.
  • “All mushrooms are safe if cooked/parboiled/dried/pickled/etc.” – While it is true that some otherwise-inedible species can be rendered safe by special preparation, many toxic species cannot be made toxin-free. Many fungal toxins are not particularly sensitive to heat and so are not broken down during cooking; in particular, α-amanitin, the poison produced by the death cap (Amanita phalloides) and others of the genus, is not denatured by heat.
  • “Poisonous mushrooms will turn rice red when boiled”.[3] – A number of Laotian refugees were hospitalized after eating mushrooms (probably toxic Russula species) deemed safe by this folklore rule and this misconception cost at least one person her life.[4][5]
  • “Poisonous mushrooms have a pointed cap. Edible ones have a flat, rounded cap.” – The shape of the mushroom cap does not correlate with presence or absence of mushroom toxins, so this is not a reliable method to distinguish between edible and poisonous species. Death cap, for instance, has a rounded cap when mature.
  • “Boletes are, in general, safe to eat” – It is true that, unlike a number of Amanita species in particular, in most parts of the world, there are no known deadly varieties of the Boletus genus, which reduces the risks associated with misidentification. However, mushrooms like the Devil’s Bolete are poisonous both raw and cooked and can lead to strong gastrointestinal symptoms, and other species like the lurid bolete require thorough cooking to break down toxins. As with other mushroomgenera, proper caution is, therefore, advised in determining the correct species.